1. Technical Field
The present disclosure relates to an auto-focus technologies, and particularly to an auto-focus method capable of finding a focused position.
2. Description of Related Art
In order to change a relative positions between a lens module and a sensing element, a camera module uses an auto-focus function uses a voice coil motor to drive the lens module, and focuses the lens module to get a sharp image. A commonly used image analytic function is a modulation transfer function (MTF). In order to improve searching for an optimum focus position, a larger searching space to calculate the MTF values one by one is used, and when the MTF value is over a peak value, a searching space is narrowed for recalculating the MTF value. The above steps are repeated until the peak value over by the MTF value no longer changes, then the auto-focus function is completed. But when the MTF curve shows a little oscillation, it is easy to search only in regional peaks, rather than a global peak. Therefore, it is necessary to provide a focus position searching method to avoid falling into a regional peak.